The cave is about 80 miles inland. It does have some light grafitti but NZ people, generally, do not mess things up. Likely some backpacking tourists from other countries. At least it's not spray painted like so many places in the US. I deplore defacing sites as it leaves nothing for the next generation to enjoy.
Most of the pic's show a shortage of trees around the cave. Was there other vegetation like brush that they used for the firewood or was there, at one time more trees and they were used up for cooking?
This is the valley below Castle Rocks. Its like a high desert with an aluvial glacier plain. Many of the native plants can be found only here and nowhere else in the world. There are lots of trees just not in this area. It gets lots of snow melt. The water is also very cold. Great Brown Trout fishin!